1. Field of the Invention
The present invention relates to a color filter substrate manufacturing method and color filter substrate used for color display devices and, more particularly, to a color filter substrate manufacturing method and color filter substrate suitable for color liquid crystal display devices used for color televisions, car televisions, personal computers and the like, and a liquid crystal element using the color filter substrate.
2. Related Background Art
With recent development of personal computers, especially portable personal computers, demand has arisen for liquid crystal displays, especially color liquid crystal displays. However, in order to further popularize the use of liquid crystal displays, a reduction in cost must be achieved. Especially, it is required to reduce the cost of a color filter. Various methods have been tried to satisfy the required characteristics of color filters while meeting the above requirements. However, any method capable of satisfying all the requirements has not been established. The respective methods will be described below.
The first method is a pigment dispersion method. In this method, a pigment-dispersed photosensitive resin layer is formed on a substrate and patterned into a single-color pattern. This process is repeated three times to obtain R, G, and B color filter layers.
The second method is a dyeing method. In the dyeing method, a glass substrate is coated with a water-soluble polymer material as a dyeable material, and the coating is patterned into a desired shape by a photolithography process. The obtained pattern is dipped in a dye bath to obtain a colored pattern. This process is repeated three times to form R, G, and B color filter layers.
The third method is an electrodeposition method. In this method, a transparent electrode is patterned on a substrate, and the resultant structure is dipped in an electrodeposition coating fluid containing a pigment, a resin, an electrolyte, and the like to be colored in the first color by electrodeposition. This process is repeated three times to form R, G, and B color filter layers. Finally, these layers are thermally cured.
The fourth method is a printing method. In this method, a pigment is dispersed in a thermosetting resin, and a printing operation is repeated three times to form R, G, and B coatings separately. Colored layers are then formed by thermosetting the resins.
In each of the above methods, a protective layer is generally formed on the colored layers.
The point common to these methods is that the same process must be repeated three times to obtain layers colored in three colors, i.e., R, G, and B. This causes an increase in cost. In addition, as the number of processes increases, the yield decreases. In the electrodeposition method, limitations are imposed on pattern shapes which can be formed. For this reason, with the existing techniques, this method cannot be applied to TFT color liquid displays. In the print method, a pattern with a fine pitch cannot be formed because of poor resolution and poor evenness.
In order to eliminate these drawbacks, methods of manufacturing color filters by an ink-jet system are disclosed in Japanese Laid-Open Patent Application Nos. 59-75205, 63-235901, 63-294503, and 1-217302.
In Japanese Laid-Open Patent Application No. 1-217302, upon exposing an ink receptive layer to a pattern, an alignment mark is formed in a region outside the effective display region and used for alignment of a coloring ink to be applied.
In this manner, in the color filter manufacturing method by an ink-jet system, the alignment mark formed in a region outside the effective display region is used for drawing alignment by the ink-jet head. Accordingly, the distance between the alignment mark and the nozzle position of the ink-jet head is long, and drawing often shifts.
In many cases, the color filter is distorted outside the effective display region, i.e., near the edge of the color filter. A large distortion obstructs proper alignment.
In order to form the alignment mark, a margin must be ensured outside the effective display region. This reduces the effective display region for displaying an image with respect to the size of the color filter substrate, and thus the substrate cannot be effectively used. Further, when a liquid crystal element is constituted using such a color filter substrate, the positional relationship with the alignment mark of a counter array substrate must be considered. This limitation complicates the design.